ASTRONOMY. 
227 
zontal. The same thing holds true of the planets; of oui 
own among the rest. We are entitled, therefore, to ask, 
and to urge the question, Why did the projectile velocity 
and projectile direction of the earth happen to be near¬ 
ly those which would retain it in a circular form ? Why 
not one of the infinite number of velocities, one of the 
infinite number of directions, which would have made it 
approach much nearer to, or recede much farther from, the 
sun? 
The planets going round, all in the same direction, and 
all nearly in the same plane, afforded to Buffon a ground 
for asserting, that they had all been shivered from the sun 
by the same stroke of a comet, and by that stroke project¬ 
ed into their present orbits. Now, besides that this is to 
attribute to chance the fortunate concurrence of velocity 
and direction which we have been here noticing, the hy¬ 
pothesis, as I apprehend, is inconsistent with the physical 
taws by which the heavenly motions are governed. If the 
olanets were struck off from the surface of the sun, they 
*vould return to the sun again. Nor will this difficulty be 
|ot rid of, by supposing that the same violent blow which 
shattered the sun’s surface, and separated large fragments 
from it, pushed the sun himself out of his place; for the 
consequence of this would be, that the sun and system 
of shattered fragments would have a progressive motion, 
which indeed may possibly be the case with our system; 
but then each fragment would, in every revolution, return 
to the surface of the sun again. The hypothesis is also 
contradicted by the vast difference which subsists between 
the diameters of the planetary orbits. The distance of 
Saturn from the sun (to say nothing of the Georgium Sidus) 
is nearly twenty-five times that of Mercury; a disparity, 
which it seems impossible to reconcile withBuffon’s scheme. 
Bodies starting from the same place, with whatever differ¬ 
ence of direction or velocity they could set off, could not 
have been found, at these different distances from the cen¬ 
tre, still retaining their nearly circular orbits. They must 
have been carried to their proper distances before they 
were projected.* 
* “ If we suppose the matter of the system to be accumulated in the 
centre by its gravity, no mechanical principles, with the assistance of 
this power of gravity could separate the vast mass into such parts as the 
sun and planets; and after carrying them to their different distances, pro¬ 
ject them in their several directions, preserving still the equality of action 
and reaction, or the state of the centre of gravity of the system. Such 
an exquisite structure of things could only arise from the contrivance and 
